Lectins are proteins which bind to carbohydrates with each lectin having a given specificity for recognizing a particular configuration of a sugar. By binding to surface components on cells, they cross-link cells and agglutination can occur. The agglutination process reflects the nature of the cell surface. Several lectins, for example, will differentially agglutinate transformed cells. Lectins, therefore, are used to detect or probe cell surface changes on cancer cells. Lectins also can induce a physiological response by cells to which they bind. A large number of lectins will induce mitogenesis in lymphocytes. In order to understand how lectins interact with cell surfaces, it is essential to understand the saccharide binding process and the factors which induce binding activity. Our studies are concentrating on two metal ion-requiring lectins, concanavalin A and a lectin from lima bean (LBL). LBL occurs in two forms. Only the larger one is highly mitogenic. The metal ion function is being examined by magnetic resonance (both NMR and ESR) spectroscopy. Part of our work will be to elucidate the metal ion requirements for LBL. Distances between the paramagnetic ion manganese and water relaxation effects will be determined. Concanavalin A is a relatively well-studied lectin and we are examining both kinetic and thermodynamic details of its metal ion binding process. The metal ion binding studies on LBL are just beginning and much of our work will be devoted to basic detail about structure. Studies on the binding of the two forms of LBL to erythrocytes, lymphocytes, normal and transformed cells, will be carried out with the purpose of defining properties which will allow LBL to be used as a cell surface probe.